1. Field of the Invention
This invention relates to the preparation of polyamides and intermediates thereto, and is more particularly concerned with novel oligomeric intermediates, which are readily converted to polyamides, and with the preparation of said oligomeric intermediates.
2. Description of the Prior Art
Polyamides and copolyamides of many diverse types have been recognized and utilized in the polymer art for many years. Beginning with the pioneer work of Carothers (see U.S. Pat. Nos. 2,071,250, 2,071,251, and 2,071,253) and continuing up to recent technology (see Encyclopedia of Polymer Sci. and Technology, Vol. 10, pp. 347-615, 1969, John Wiley & Sons, New York, N.Y.,) many polyamide compositions have been disclosed. The prior art discloses a variety of methods for preparing polyamides including the melt condensation technique (see U.S. Pat. No. 3,651,022) of a diamine with a dicarboxylic acid; the amine-salt technique (see Preparative Methods of Polymer Chemistry, W. R. Sorenson, et al., p. 62, 1961, Interscience Pub. Inc., New York, New York) wherein the diamine and diacid are prereacted to form the crystalline amine-carboxylate salt prior to polymerization; the reaction of a diamine with a diacid chloride (see U.S. Pat. No. 3,063,966); and the reaction of a diisocyanate with a diacid (see U.S. Pat. No. 3,642,715). While all the methods referred to hereinabove provide polyamides and copolyamides in good yield, purity and molecular weight, they do not provide for any type of prepolymer technology and the advantages to be derived therefrom.
I have now found a novel class of oligomeric poly[.alpha.,.omega.-dicarboxyalkylene-N,N'-dicarboxy(diaminoarylene)-anhy drides] which are easily prepared and storage stable. These novel oligomers serve as prepolymers for the formation of the corresponding poly or copolyamides by the evolution of carbon dioxide. Further, this method of preparing polyamides provides a technique for obtaining easily other types of polymers such as polyurethanes, polyureas, polycarbodiimides, etc., copolymerized with the polyamides, which method has not been available heretofore using any of the prior art methods.